| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2016) | |
| Thin Films | Wednesday Sessions |
| Session TF-WeE |
| Session: | Microstructure & Surface Morphological Evolution in Organic & Inorganic Films |
| Presenter: | Virginia Anderson, US Naval Research Laboratory, USA |
| Authors: | V.R. Anderson, US Naval Research Laboratory, USA N. Nepal, US Naval Research Laboratory, USA S.D. Johnson, US Naval Research Laboratory, USA Z.R. Robinson, The College at Brockport SUNY, USA A. Nath, US Naval Research Laboratory, USA A. Kozen, US Naval Research Laboratory, USA A. DeMasi, Boston University, USA J.K. Hite, US Naval Research Laboratory, USA K.F. Ludwig, Boston University, USA C.R. Eddy, Jr., US Naval Research Laboratory, USA |
| Correspondent: | Click to Email |
A focus area of research on III-nitrides attempts to lower the growth temperature of films, because molecular beam epitaxy and metalorganic chemical vapor deposition (MOCVD) must be done at relatively high temperatures to produce a high quality material. As an example, aluminum nitride MOCVD takes place at over 1000°C. Tunable band gaps, high breakdown voltages, and piezoelectric properties are attractive qualities of aluminum nitride films, and thus motivate the search for alternate fabrication methods. Atomic layer epitaxy (ALE) of GaN, AlN, and InN films have been shown at temperatures far below that required for MOCVD. [1] Further exploration of the growth parameters of these films is underway. Research during the actual growth process allows much more information on early stages of film deposition, and eliminates many of the ex-situ issues with surface oxidation upon sample removal from the reactor. The X-ray photons available at some synchrotrons allow insight into the growth process from grazing incidence small angle X-ray scattering (GISAXS), a technique that can be carried out at ALE pressures and is extremely sensitive to surface morphological evolution.
The work presented will describe film growth of aluminum nitride using trimethylaluminum and a nitrogen/argon or hydrogen/nitrogen/argon plasma. Based on ex-situ examinations, aluminum nitride ALE on MOCVD GaN at 500°C was previously seen to exhibit single crystal character, with a full-width at half maximum of 670 arc-seconds. [2] Work presented here describes results on changing the temperature and the plasma conditions for ALE AlN. The substrates were sapphire and the growth took place at Brookhaven National Laboratory and at the Cornell High Energy Synchrotron Source in a custom reactor designed to facilitate GISAXS monitoring during growth.
These results suggest that surface feature distances are related to the final quality of the aluminum nitride films. Samples grown at 350-400°C have higher impurities than samples grown at 450-500°C, and GISAXS shows closer features at the lower temperatures. In addition, holding the flow constant and changing the nitrogen to argon ratio resulted in changes in the atomic species present in the plasma source, and changes in nucleation and growth behavior.
References:
1 N. Nepal et al., Thin Solid Films 589 47 (2015)
2 N. Nepal et al., Appl. Phys. Lett. 103 0 82110 (2013)